RFR: 8252888: Simplify G1MMUTracker class hierarchy [v2]

[Stefan Johansson]

On Mon, 21 Sep 2020 22:02:16 GMT, John Tortugo <github.com+2249648+JohnTortugo at openjdk.org> wrote:

>> Relates to: https://bugs.openjdk.java.net/browse/JDK-8252888
>> Tested on: x86_64 - Linux - tier1
>> Need sponsor: yes
>> 
>> Merge `G1MMUTracker` and `G1MMUTrackerQueue` into a single class and make method members non virtual.
>
> John Tortugo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rename MMUTrackerQueue[Element] to MMUTracker

Thanks for doing this cleanup.

Looks good, please just do a small change to one of the comments.

src/hotspot/share/gc/g1/g1MMUTracker.hpp line 55:

> 53:
> 54: // This implementation uses a fixed-size queue to keep track of all
> 55: // recent pause times. Two major user controls over G1 behavior are

I would move the first sentence down to right before the warning about seconds. I would also change it to something
like: `The G1MMUTracker uses a fixed-size queue to keep track of all recent pause times. The pause time data is used to
avoid breaking the MMU.`

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Changes requested by sjohanss (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/214